Composite materials have been shown to have a variety of practical uses. The reinforced or "filled" plastics constitute an important and useful class of composite materials; such materials consist of an organic polymer matrix, within which there is dipersed an inorganic solid, typically in the form of fibers, flakes, spheres, or fine particles. A variety of materials, including paint films, adhesives, colored plastics, and compounded rubbers, are, in fact, composite materials in this sense.
Each of the components contributes characteristic properties to the resulting composite material. The polymer contributes ease of shaping, cohesiveness, impact resistance, flexibility, etc. The inorganic solid contributes rigidity and dimensional stability, and possibly certain more specialized properties such as opacity, color, electrical conductivity, chemical and thermal stability, etc.
In many cases of practical importance, the inorganic component is an oxide or mixture of oxides. Typical examples include silica alumina, glass, talc, and pigments such as zinc oxide and titanium dioxide.
In preparing and fabricating composite materials, it is customary to disperse the inorganic solid in a molten polymer or polymer solution, to shape the resulting mixture and/or apply it to a supporting surface, and to allow the mixture to solidify by cooling or by solvent evaporation. Alternatively, the inorganic solid may be dispersed in an organic monomer, prepolymer, or mixture or solution thereof; the resulting dispersion is shaped or applied to a supporting surface, and the preparation of the composite material is then completed by polymerization in situ.